Phosphane-borane complex

Tetrasubstituted phosphinous amides of the type R2NPPh2 have been successfully arylated at phosphorus by the action of bromobenzene, in a process catalyzed by NiBr2, to give the aminophosphonium bromides [R2NPPh3] Br [109]. Other representative members of this class form phosphane-borane complexes [62], are aminated at phosphorus by chloramine to yield bis(amino)phos-phonium salts [110] and have been claimed to be protonated at phosphorus by ethereal tetrafluoroboric acid, as determined by NMR analysis [111]. 

Faure et al92 reported the first enzymatic resolution of phosphane-borane complex. Thus, the borane adduct of (2-hydroxypropyl)diphenylphosphane 107 was resolved using the lipase CAL-B and vinyl acetate as acyl donor in organic solvent. The remaining unreacted substrate (.S )-107 was recovered with 91 % ee. 

Figure 52 Lipase-catalysed kinetic resolution of a phosphane-borane complex 107.

In 2011, Takeda Pharmaceutical Co. Ltd. developed a protocol for the manufacturing process of the squalene synthase inhihitor TAK-475 [143]. This group used air-stable phosphane-borane complexes (Ar2PH-BH3) and prepared a series of up to 30 BINAP analogs, using basically the Merck conditions [141]. 

Figure 1.52. Racemic fullerenyl-substituted phosphane ( )-244, and stereoisomerically pure P-chiral fullerenyl-substituted phosphinites 245 and 246, obtained via addition to Cgo of diastereoisomerically pure, (+)-menthyl phosphinite-borane complexes 247 and 248, respectively.

The sign of /C( Sn, P) is negative in all tin-phosphorus compounds (dominant influence of the lone pair of electron at the phosphorus atom), except of phosphane adducts of tin(IV) halides. Even in transition metal complexes of stannylphosphanes or in borane complexes of stannylphosphanes the coupling sign does not change, although the phosphorus lone pair of electrons is engaged. 

Polymer-bound piperazine can also be used for the deprotection of phosphane-, phosphate- and phosphinite-borane complexes to give the corresponding free... 

Thanks to this general procedure, some classes of tetrathiahehcene-based alkyl and aryl phosphorous derivatives are now available, including phosphine—borane complexes (2015JO3921), phosphanes (2011EJO5649, 2013IC7995), phosphine oxides (2014EJO2694), and a diphosphonate (2011EJO5649). 

Recently, this group published a route to new water-soluble, aliphatic phosphanes that build complexes of the same structure as 13 (109). Cy2P (CH2)2N(CH3)3Cr. Cy2P(CH2)2S03Na+, and others were prepared from air-stable, borane-protected precursors. The steric and electronic parameters of these new phosphanes were investigated. 

Boron-nitrogen and boron-phosphorous compounds are classical textbook examples of donor-acceptor complexes. The chemical bonds of the Lewis-acid Lewis-base complexes are usually explained in terms of frontier orbital interactions and/or quasiclassical electrostatic attraction in the framework of the Hard and Soft Acid and Base (HSAB) model [73]. We were interested in seeing if the differences between the bond strengths of boron-nitrogen and boron-phosphorous complexes for different boranes, amines and phosphanes can be explained with the EDA method. 

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